I'd like to give folks a few updates on fabrics since I wrote this, in particular the 150D cuben hybrid. Meredith has been using the pack shown in the bottom photo all year, most notably a longer technical trip in the Grand Canyon, as good a test as any for a heavier use fabric.
To provide more details, the front and sides of that pack are cuben hybrid. The bottom is a single layer of VX42. The bottom of the side panels (below the side pockets) is a double layer of cuben hybrid. The seam joining the VX42 and cuben hybrid (transitioning from the bottom to the front) was double stitched, felled, and double stitched again.
After the Grand Canyon trip a steady line of small holes were visible 5mm or so above said seam in the cuben of the front panel. The scarp of VX42 I had at the time was only so big, and ideally would have wrapped up another few inches. I am convinced that while the 150D cuben hybrid is a great fabric (the waterproofing really is impressive) the modest abrasion resistant coupled with the cost makes it difficult to recommend. For me.
If you don't beat on things so much it will surely hold up just fine, but I'd suggest considering X33 instead. Weight is comparable, waterproofing is equivalent, as is abrasion resistance. X33 is quite a bit more flexible and quiet than hybrid cuben, and in the only color currently available at retail (multicam, sadly) somewhat translucent, making dark corners easy to explore for small items. I've made two packs with it in the past six months, and have been quite pleased. The one I took on the aforementioned trip survived unscathed, though it did have a 1000D cordura bottom and 2-3" of reinforcement up the front and sides.